The present invention is related to a navigation apparatus for displaying a drive position of an automobile and the like on a map based upon information acquired from a GPS (Global Positioning System).
Recently, navigation apparatus are rapidly popularized, while the navigation apparatus measure current locations based upon information acquired from the GPS, and read out map data containing these current locations from a CD-ROM and the like so as to display map images where the current locations are located at a center.
This type of navigation apparatus not only displays a current location on a map, but also calculates an optimum route defined from a departure place up to a destination place, and then sequentially guides a route in response to current locations in either a voice manner or a display manner, as disclosed in, for example, Japanese Patent Publication No. Hei. 11-344355.
As this guidance mode, with respect to a present road link, the navigation apparatus judges direction/angle/distance up to a crossing as to such a road link where the own vehicle is planned to be turned. When the own vehicle is located at a predetermined point in front of the crossing, the navigation apparatus reproduces by a speaker, such a message, for example, xe2x80x9cApproximately 300 meters ahead, please proceed in the oblique left directionxe2x80x9d, and xe2x80x9cSoon after, please turn to the left. Take care of your drive.xe2x80x9d
However, in accordance with the above-explained arrangement, when the own vehicle enters into, for example, a tunnel and thus cannot receive signals transmitted from the GPS satellites, since the current location cannot be measured, the navigation apparatus cannot judge a point where a voice guidance is made, so that the voice guidance cannot be performed as explained above. In particular, in the case that there are an exit of a superhighway and a direction turning point on the guidance route in the vicinity of the exit of the tunnel, since no voice guidance is made, there is a certain case that the own vehicle may mistakenly pass through this exit of the superhighway and the direction turning point.
The present invention has been made to solve the above-explained problem, and is to provide such a navigation apparatus by which when signals transmitted from GPS satellites cannot be received, and also when a current location is located on a guidance route during a calculation time period after the signals transmitted from the GPS satellites have been received, a virtual current location is displayed in such a manner that the virtual current location is moved on the guidance route at a predetermined speed, and then, a guidance is notified in response to this virtual current location.
Also, in another navigation apparatus of the present invention, in the case that a starting point of a tunnel is detected as a current location, if the current location is located on the guidance route, then a virtual current location is displayed in such a manner that the virtual current location is moved on the guidance route at a predetermined speed, and a guidance is notified every predetermined guidance point.
Also, another navigation apparatus of the present invention is featured by that a virtual current location is displayed in such a manner that the virtual current location is moved on the guidance route after an end point of the tunnel has been detected as a current location until signals transmitted from GPS satellites are received to output a calculation result of the current location, and the guidance notification is continued in response to the virtual current location.